What is Dark Matter and Dark Energy

 Dark Energy and Dark Matter

Since our universe, or we can say earth, sun and other stars are mainly composed of tiny subatomic particles called electrons, protons and neutrons and other particles as well thus named as Baryonic matter. They are jumbled together and make the whole universe. 

They make up almost 5% of the universe, then what about remaining 95% of the universe? What comes in this 95%? In the near 20th century, it was found that about 25% of the universe the composed of an invisible substance called Dark Matter, and the force that repel gravity is known as Dark Energy which constitute about 70% of the universe.

This dark matter does not interact with baryonic matter (matter that makes up stars and other celestial bodies that reflect light.) and thus it does not reflect the light and therefore, scientists are unable to see the dark matter with present instruments. Various scientists say that it exerts a gravitational pull on the galaxies. 

According to standard Physics, stars should travel slowly at the edges of the spiral galaxy than those at the center of the galaxy where most of the galaxy’s matter is concentrated. But they observed that stars were travelling with almost same speed irrespective of their location, where are they. This leads them to think that there is something invisible, which is exerting a force. They called it Dark Matter. Now the question arises here is “Is Dark Matter useful?” 

Yes it is helpful in various aspects, one of them is it helps in understanding the gravitational lensing which means a phenomenon in which the light from distant object is bent the gravity of a massive black hole or a galaxy. This enables scientists to explain the strange rings and arcs of light generally take place. Some scientists are continuously trying to solve the mystery of the dark matter they made a hypothesis that dark matter is kind of matter that do not interact with light or other matter. Several organizations are trying to get dark matter that can be studied under labs. 

The unexpected discovery of dark energy in the 1990s came as a shock to scientists, as it defied the assumption that gravity would cause the universe's expansion to slow down. Instead, it was revealed that the expansion was speeding up. Scientists believe that this accelerated expansion is caused by a repulsive force resulting from quantum fluctuations in empty space, and this force appears to become stronger as the universe expands. Unlike dark matter, the origin of dark energy remains a mystery. Some scientists suggest that dark energy may be a fifth fundamental force known as quintessence, while others propose that it may be consistent with a cosmological constant, a concept introduced by Albert Einstein and later abandoned. Although explaining the accelerated expansion of the universe by adding dark energy as a cosmological constant could be an elegant solution, the reason for the existence of this enigmatic force remains unknown to scientists.

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